what is the diference between DVD+RW and DVD-RW?

Answer 1

DVD+RW --- is a ReWriteable media format of the DVD+R standard

DVD-RW --- Short for DVD-ReWritable, a re-recordable DVD format similar to DVD+RW. The data on a DVD-RW disc can be erased and recorded over numerous times without damaging the medium. DVD-R, DVD-RW and DVD-RAM are supported by Panasonic, Toshiba, Apple Computer, Hitachi, NEC, Pioneer, Samsung and Sharp. These formats are also supported by the DVD Forum.

Answer 2

A designation related to dual layer. Player/recorders are multi format. The difference is what is recorded in what if your dvd unit is limited.